Who is "really" running email?

Email on the internet was originally designed in a decentralized fashion. However this decentralized deployment may not be evenly distributed. There is a supposed perception that email services are increasingly serviced on hosted digital infrastructure, which are largely managed by a small number of parties. GMail, Outlook, iCloud Mail, Yandex Mail, and other brand names are supposedly increasingly responsible for email services on the internet.

Earlier studies looking into centralization and consolidation of email on the internet, were based on analysis of the MX records (referring to SMTP servers) in use by lists of names, such as the Tranco list or zone files of TLDs. These studies give good insight into how many domains are serviced by email providers, but do not reveal anything about whether those providers are actually used and to what extent. For example the cloud services provider OVH is the most prevalent email provider in the .fr zone, but an MX record for OVH is automatically deployed when registering a domain name with them, even if that name will only be used for web.

To get better insight into how much of those email providers are really being used, one would need access to the query volume for those MX records. In this talk we try to provide better insight into the actual usage of those email service providers, by analysis of the MX queries at one of the pops of the popular public Quad9 resolver (9.9.9.9), with which we have a partnership for this study.